Novel 5-chloro-1,3,2-oxazaphosphorine (A) and 3-chloro-1,5, 2-oxazaphosphorine (B) derivatives, which are proposed as biological alkylating agents with increased membrane transprt properties, will be synthesized for screening tests as improved anticancer drugs. The possibility of enantiomer-specific cytotoxicity for these new chiral systems and for the known anticancer drug cyclophosphamide (CPA) will also be studied by screening tests on individual enantiomers. Adaptation of available synthetic techniques and the use of new ring-closure methods are proposed for construction of A and B derivatives. Enantiomerically pure samples of the four possible stereoisomers of 2-oxo-2-methyl-A and the enantiomers of CPA will be isolated by a combination of resolution and stereospecific synthesis methodology.